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Title: Establishing Vadose Zone Slow-Release Carbon Sources for Enhanced Bioremediation Using Silica Suspension

Delivery of C sources (nutrients) to the vadose zone and establishing a slow-release C source in this unsaturated zone are essential for promoting long-term, enhanced contaminant bioremediation at sites with deep vadose zones, such as the Hanford Site in the southeast of the state of Washington. Conventional solution-based injection and infiltration approaches face challenges in achieving delivery goals. Aqueous colloidal silica suspension has characteristics that can potentially be used for nutrient delivery and slow-release source setup. This research was conducted to (i) demonstrate delayed gelation of colloidal silica suspensions with the presence of nutrients; (ii) prove that gelation takes place in sediment and the gel slowly releases nutrients; and (iii) show that silica suspensions are injectable for vadose zone emplacement. Results demonstrated that nutrient-laden colloidal silica suspensions have low initial viscosity and then increase in viscosity with time until reaching gelation, allowing for a slow release of nutrients into the environment. Higher salt and silica concentrations increased the rate of viscosity climbing and the rate of gelation, whereas higher silica concentrations resulted in stronger gels. Nutrients were slowly released from gels in both batch and column experimental settings. The rheological and injection behavior of the silica suspensions revealed the injectabilitymore » of these fluids. This study demonstrated that colloidal silica suspension could be used as a carrier to distribute nutrients to the vadose zone and to establish slow-release nutrient sources.« less
 [1] ;  [1] ;  [2]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Energy and Environment Directorate
  2. Chinese Academy of Sciences (CAS), Beijing (China). Inst. of Process Engineering
Publication Date:
Report Number(s):
Journal ID: ISSN 1539-1663
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Vadose Zone Journal
Additional Journal Information:
Journal Volume: 17; Journal Issue: 1; Journal ID: ISSN 1539-1663
Soil Science Society of America
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier: